lightningd: make sure non-stub channels always have a local alias.

If we pull and old channel from the database, it might not.

Fixes: ElementsProject#7645
Changelog-Fixes: lightningd: crash when starting channeld for older channel with no local alias.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/channel.c

@@ -17,6 +17,7 @@
 #include <lightningd/opening_common.h>
 #include <lightningd/peer_control.h>
 #include <lightningd/subd.h>
+#include <sodium/randombytes.h>
 #include <wallet/txfilter.h>
 #include <wire/peer_wire.h>
 
@@ -444,6 +445,11 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->remote_channel_ready = remote_channel_ready;
 	channel->scid = tal_steal(channel, scid);
 	channel->alias[LOCAL] = tal_steal(channel, alias_local);
+	/* We always make sure this is set */
+	if (!channel->alias[LOCAL]) {
+		channel->alias[LOCAL] = tal(channel, struct short_channel_id);
+		randombytes_buf(channel->alias[LOCAL], sizeof(struct short_channel_id));
+	}
 	channel->alias[REMOTE] = tal_steal(channel, alias_remote);  /* Haven't gotten one yet. */
 	channel->cid = *cid;
 	channel->our_msat = our_msat;

lightningd/opening_control.c

@@ -104,7 +104,6 @@ wallet_commit_channel(struct lightningd *ld,
 	s64 final_key_idx;
 	u64 static_remotekey_start;
 	u32 lease_start_blockheight = 0; /* No leases on v1 */
-	struct short_channel_id *alias_local;
 	struct timeabs timestamp;
 	bool any_active = peer_any_active_channel(uc->peer, NULL);
 
@@ -166,9 +165,6 @@ wallet_commit_channel(struct lightningd *ld,
 	else
 		static_remotekey_start = 0x7FFFFFFFFFFFFFFF;
 
-	alias_local = tal(NULL, struct short_channel_id);
-	randombytes_buf(alias_local, sizeof(struct short_channel_id));
-
 	channel = new_channel(uc->peer, uc->dbid,
 			      NULL, /* No shachain yet */
 			      CHANNELD_AWAITING_LOCKIN,
@@ -186,7 +182,7 @@ wallet_commit_channel(struct lightningd *ld,
 			      local_funding,
 			      false, /* !remote_channel_ready */
 			      NULL, /* no scid yet */
-			      alias_local, /* But maybe we have an alias we want to use? */
+			      NULL, /* Will assign random alias */
 			      NULL, /* They haven't told us an alias yet */
 			      cid,
 			      /* The three arguments below are msatoshi_to_us,